1. Field of the Invention
This invention relates to an etch process useful in the manufacture of integrated circuit structures. More particularly, this invention relates to an etch process for simultaneous removal of photoresist and etch residues remaining from a metal silicide and/or polysilicon etch.
2. Description of the Related Art
In the construction of an integrated circuit structure on a substrate, etching of a masked polysilicon layer, for example, to form polysilicon lines on the structure, or the etching of a dual layer (polycide) structure comprising a metal silicide layer and a polysilicon layer to form dual layer lines on the integrated circuit structure, can result (in either case) in the formation of etch residues, such as, for example, sidewall deposits on the sidewalls of the polysilicon or metal silicide/polysilicon lines.
For example, as shown in FIG. 1, when a line 10 (which may comprise either a polysilicon line or a dual layer polycide line structure) is formed over a gate oxide layer 6 on a silicon semiconductor wafer 2, by patterning a photoresist layer to form a photoresist mask 14 and then anisotropically etching an underlying polysilicon and/or polycide layer through the mask, a residue 20a may form on the sidewalls of line 10, and a similar residue 20b may form on the sidewalls of photoresist mask 14.
Such etch residues may, for example, comprise SiBr.sub.x or SiCl.sub.y etch products or a silicon-rich oxide, SiO.sub.x. However, in any event, the residues must be removed from the integrated circuit structure, since they often interfere with the subsequent formation of other materials on the structure, due to their poor adherence and possible contamination of other materials.
Conventionally, such etch residues have been removed by wet etching with dilute HF solutions. However, since HF will also attack gate oxide, monitoring of the wet etch is very important. Amini et al. U.S. Pat. No. 5,030,590, issued Jul. 9, 1991, and assigned to the assignee of this invention, proposed the use of a hydroxide wet etch instead of HF to reduce the damage to oxide portions of the structure.
Subsequently, in Webb et al. U.S. Pat. No. 5,228,950, issued Jul. 20, 1993, and assigned to the assignee of this invention, it was proposed to substitute a dry etch process for the previously used wet etch processes. Webb et al. taught the use of an NF.sub.3 plasma etch, to remove oxide-containing deposits, such as the residues shown in FIG. 1, previously formed on the sidewalls of polysilicon lines and the sidewalls of the overlying photoresist during the etching of the polysilicon. The dry residue-removal etch process was conducted in the same chamber used for the polysilicon etch, i.e., before removal of the substrate to another chamber for removal of the photoresist. The Webb et al. patent states that the NF.sub.3 etchant gas may be used alone or in combination with one or more additional reactive gases such as SF.sub.6, Cl.sub.2, and CF.sub.4, as well as one or more carrier gases such as helium, oxygen, or argon, using a plasma ignited in the etch chamber.
While such a dry etch process will remove the etch residues remaining from a polysilicon/polycide etch, it does introduce an additional step into the process after the polysilicon/polycide etch step, and prior to the photoresist removal step. It would, therefore, be advantageous if the etch residues from the polysilicon and/or polycide etch could be removed without the need for an additional cleaning step, for example, if such residues could be removed simultaneously with the removal of the photoresist mask over the etched polysilicon and/or polycide, thus eliminating the additional cleaning step.